Silent cerebral ischaemia: hidden fingerprints of invasive medical procedures

Ascertainment of any and all neurologic and myocardial damage in carotid revascularization: the key to optimization?

The majority of carotid revascularization procedures performed at present are in asymptomatic patients. Since such procedures convey no immediate benefit, but rather protect from future hazard, optimization of procedural safety is mandatory. The authors focus their discussion on the methodologies that assess periprocedural myocardial damage and brain injury, as used in past clinical trials, from the fields of perioperative medicine and neurovascular imaging, and discuss methodologies to reduce both events in carotid revascularization.

Neuroform stent-assisted treatment of intracranial aneurysms: long-term follow-up study of aneurysm recurrence and in-stent stenosis rates

INTRODUCTION

Our purpose was to analyze the long-term evolution of wide neck cerebral aneurysms treated with stent assistance.

METHODS

Data of consecutive patients treated with the Neuroform stent over 9 years were retrospectively analyzed with emphasis on periprocedural complications, aneurysm occlusion grade evolution, and in-stent stenosis rates.

RESULTS

Altogether, 113 patients with 117 unruptured and ruptured aneurysms were subject of analysis. Mean aneurysm size was 9.4 mm, and mean neck size was 4.7 mm. Procedural thromboembolic and hemorrhagic complications affected eight (6.8%) and four cases (3.4%), respectively. Immediate complete occlusion and occlusion with residual neck was achieved in 85% of cases, which at the first follow-up of 6 months, changed to 77 and 76 % at 36 months. Aneurysms ≥10 mm showed a higher tendency of recurrence. During the overall follow-up time ranging from 1 to 9 years, an in-stent stenosis of ≥50 % was observed only in three cases, all of them being asymptomatic.

CONCLUSIONS

Stent-assisted coiling of wide neck aneurysms provided stable occlusion over the long-term follow-up, with very low and silent in-stent stenosis rates. Some incompletely occluded aneurysms showed a tendency of progressive occlusion; however, this was counterbalanced by the regrowth of others.

Cognitive Outcome and Clinically Silent Thromboembolic Events After Coiling of Asymptomatic Unruptured Intracranial Aneurysms

BACKGROUND:

Thromboembolic events are the most common complication after coiling of unruptured intracranial aneurysms (UIAs). However, it remains unclear whether these clinically silent ischemic lesions (CSILs) have any clinical significance.

OBJECTIVE:

To evaluate cognitive outcome after coil embolization of asymptomatic UIAs and its relationship with CSILs after the procedure.

METHODS:

We prospectively enrolled 40 UIA patients who showed no new focal neurological deficit after coil embolization. CSILs were assessed with diffusion-weighted imaging (DWI) within 1 day after the procedure. A battery of neuropsychological tests was performed 3 times: preoperatively and postoperatively at 1 and 4 weeks after coil embolization.

RESULTS:

The incidence of cognitive impairment after coiling in patients with UIAs was 44% (17 of 39) at 1 week and 19% (7 of 37) at 4 weeks after coil embolization. DWI within 1 day after coil embolization revealed that 60% of patients (24 of 40) showed CSILs. However, no significant difference was found in any mean cognitive scores or in the number of cognitively impaired variables between patients with and without CSILs at weeks 1 and 4. Additional correlation analysis revealed no correlations between the number of CSILs on DWI and the cognitive sum z score at both 1 and 4 weeks.

CONCLUSION:

Exhaustive neuropsychological evaluation of UIA patients who underwent coil embolization demonstrated recovery or improvements from baseline cognitive function after 4 weeks, although some patients still showed cognitive deficits at 4 weeks after the procedure. However, we found no statistically significant relationship between the presence and number of CSILs on DWI and cognitive changes after the procedure.

TLR9 bone marrow chimeric mice define a role for cerebral TNF in neuroprotection induced by CpG preconditioning

Systemic preconditioning with the TLR9 ligand CpG induces neuroprotection against brain ischemic injury through a tumor necrosis factor (TNF)-dependent mechanism. It is unclear how systemic administration of CpG engages the brain to induce the protective phenotype. To address this, we created TLR9-deficient reciprocal bone marrow chimeric mice lacking TLR9 on either hematopoietic cells or radiation-resistant cells of nonhematopoietic origin. We report that wild-type mice reconstituted with TLR9-deficient hematopoietic cells failed to show neuroprotection after systemic CpG preconditioning. Further, while hematopoietic expression of TLR9 is required for CpG-induced neuroprotection it is not sufficient to restore protection to TLR9-deficient mice that are reconstituted with hematopoietic cells bearing TLR9. To determine whether the absence of protection was associated with TNF, we examined TNF levels in the systemic circulation and the brain. We found that although TNF is required for CpG preconditioning, systemic TNF levels did not correlate with the protective phenotype. However, induction of cerebral TNF mRNA required expression of TLR9 on both hematopoietic and nonhematopoietic cells and correlated with neuroprotection. In accordance with these results, we show the therapeutic potential of intranasal CpG preconditioning, which induces brain TNF mRNA and robust neuroprotection with no concomitant increase in systemic levels of TNF.

Selective factor XIIa inhibition attenuates silent brain ischemia: application of molecular imaging targeting coagulation pathway

OBJECTIVES

The purpose of this study was use molecular imaging targeting coagulation pathway and inflammation to better understand the pathophysiology of silent brain ischemia (SBI) and monitor the effects of factor XIIa inhibition.

BACKGROUND

SBI can be observed in patients who undergo invasive vascular procedures. Unlike acute stroke, the diffuse nature of SBI and its less tangible clinical symptoms make this disease difficult to diagnose and treat.

METHODS

We induced SBI in mice by intra-arterial injection of fluorescently labeled microbeads or fractionated clot into the carotid artery. After SBI induction, diffusion-weighted magnetic resonance imaging was performed to confirm the presence of microinfarcts in asymptomatic mice. Molecular imaging targeting the downstream factor XIII activity (single-photon emission computed tomography/computed tomography) at 3 h and myeloperoxidase activity (magnetic resonance imaging) on day 3 after SBI induction were performed, without and with the intravenous administration of a recombinant selective factor XIIa inhibitor derived from the hematophagous insect Triatoma infestans (rHA-Infestin-4). Statistical comparisons between 2 groups were evaluated by the Student t test or Mann-Whitney U test.

RESULTS

In SBI-induced mice, we found abnormal activation of the coagulation cascade (factor XIII activity) and increased inflammation (myeloperoxidase activity) close to where emboli lodge in the brain. rHA-Infestin-4 administration significantly reduced ischemic damage (53% to 85% reduction of infarct volume, p < 0.05) and pathological coagulation (35% to 39% reduction of factor XIII activity, p < 0.05) without increasing hemorrhagic frequency. Myeloperoxidase activity, when normalized to the infarct volume, did not significantly change with rHA-Infestin-4 treatment, suggesting that this treatment does not further decrease inflammation other than that resulting from the reduction in infarct volume.

CONCLUSIONS

Focal intracerebral clotting and inflammatory activity are part of the pathophysiology underlying SBI. Inhibiting factor XIIa with rHA-Infestin-4 may present a safe and effective treatment to decrease the morbidity of SBI.

Cerebral embolization during transcatheter aortic valve implantation: a transcranial Doppler study

BACKGROUND

Transcatheter aortic valve implantation (TAVI) is associated with a higher risk of neurological events for both the transfemoral and transapical approach than surgical valve replacement. Cerebral magnetic resonance imaging has revealed more new, albeit clinically silent lesions from procedural embolization, yet the main source and predominant procedural step of emboli remain unclear.

METHODS AND RESULTS

Eighty-three patients underwent transfemoral (Medtronic CoreValve [MCV(TF)], n=32; Edwards Sapien [ES(TF)], n=26) and transapical (ES(TA): n=25) TAVI. Serial transcranial Doppler examinations before, during, and 3 months after TAVI were used to identify high-intensity transient signals (HITS) as a surrogate for microembolization. Procedural HITS were detected in all patients, predominantly during manipulation of the calcified aortic valve while stent valves were being positioned and implanted. The balloon-expandable ES prosthesis caused significantly more HITS (mean [95% CI]) during positioning (ES(TF), 259.9 [184.8-334.9]; ES(TA), 206.1[162.5-249.7]; MCV(TF), 78.5 [25.3-131.6]; P<0.001) and the self-expandable MCV prosthesis during implantation (MCV(TF), 397.1 [302.1-492.2]; ES(TF), 88.2 [70.2-106.3]; ES(TA), 110.7 [82.0-139.3]; P<0.001). Overall, there were no significant differences between transfemoral and transapical TAVI or between the MCV and ES prostheses. No HITS were detected at baseline or 3-month follow-up. There was 1 major procedural stroke that resulted in death and 1 minor procedural stroke with full recovery at 3-month follow-up in the MCV group.

CONCLUSIONS

Procedural HITS were detected by transcranial Doppler in all patients. Although no difference was observed between the transfemoral and the transapical approach with the balloon-expandable ES stent valve, transfemoral TAVI with the self-expandable MCV prosthesis resulted in the greatest number of HITS, predominantly during implantation.

2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design

This is a report of the Heart Rhythm Society (HRS) Task Force on Catheter and Surgical Ablation of Atrial Fibrillation, developed in partnership with the European Heart Rhythm Association (EHRA), a registered branch of the European Society of Cardiology and the European Cardiac Arrhythmia Society (ECAS), and in collaboration with the American College of Cardiology (ACC), American Heart Association (AHA), the Asia Pacific Heart Rhythm Society (APHRS), and the Society of Thoracic Surgeons (STS). This is endorsed by the governing bodies of the ACC Foundation, the AHA, the ECAS, the EHRA, the STS, the APHRS, and the HRS.

A preliminary prediction model with MR plaque imaging to estimate risk for new ischemic brain lesions on diffusion-weighted imaging after endarterectomy or stenting in patients with carotid stenosis

BACKGROUND AND PURPOSE

Findings on MR imaging of carotid plaques correlate with histologic findings and may be useful in identifying vulnerable plaques. The objective of this study was to show how MR imaging findings and clinical factors could be used to construct a preliminary model and a nomogram for predicting the risk of new ischemic lesions on DWI following CEA or CAS.

MATERIALS AND METHODS

One hundred four patients with carotid stenosis undergoing treatment (63 CEA, 41 CAS) were prospectively enrolled (mean age, 71.7 ± 7.0 years; 11 women). T1-SIR and T2-SIR of carotid plaque were measured on MR imaging. Associations among carotid MR imaging findings, treatment procedures, degree of stenosis, cardiovascular risk factors, and occurrence of new ischemic lesions on DWI 1 day after treatment were studied by multivariate logistic regression.

RESULTS

One stroke occurred after CAS (2.4%), and none after CEA. New DWI lesions after treatment were observed in 25 patients (24%). Our preliminary prediction model demonstrated that T1-SIR (OR [per 0.5 increase], 3.99; 95% CI, 2.18-7.31; P < .0001) and CAS (OR, 2.06; 95% CI, 1.01-4.24; P = .048 compared with CEA) were positively associated with new DWI lesions on posttreatment DWI scans. T2-SIR (OR [per 0.5 increase], 0.74; 95% CI, 0.55-0.98; P = .037) was negatively associated. The C-index of this model was 0.79 (95% CI, 0.69-0.89), which indicated some utility in predicting the response.

CONCLUSIONS

Our preliminary prediction model and nomogram may provide an individualized risk estimate of new ischemic lesions after CEA or CAS and useful information for decision-making regarding treatment strategy.

[Silent brain infarcts]

Silent brain infarctions are frequently found by modern cerebral imaging. Up to 30% of persons without a clinical history of stroke were found to have silent brain infarction in epidemiological studies. "Silent" refers to ischemic brain lesions for which no matching clinical syndrome can be found based on history or clinical investigation. Age, education, and ethnic background have a strong impact on noticing and reporting stroke symptoms. The current clinical definition of stroke is insensitive for cognitive deficits which can also be caused by brain infarctions. The majority of silent brain infarctions are localized in the subcortical white matter of the brain; however, about 10% of silent brain infarctions are cortical. Silent brain infarctions are strongly associated with stroke risk factors and comorbidities that are known to cause clinically overt stroke. Silent brain infarctions are 5 to 10 times more frequent than clinically overt strokes. Silent brain infarctions as defined by DWI lesions on MRI imaging are a frequent finding during operative or interventional procedures and their monitoring may help improve the respective techniques in order to decrease the risk of periprocedural stroke.

New ischemic brain lesions on diffusion-weighted MRI after carotid artery stenting with filter protection: frequency and relationship with plaque morphology

BACKGROUND AND PURPOSE

CAS carries an inherent risk of distal cerebral embolization, precipitating new brain ischemic lesions and neurologic symptoms. Our purpose was to evaluate the frequency of new ischemic lesions found on DWI after protected CAS placement and to determine its association with plaque morphology.

MATERIALS AND METHODS

Fifty patients (mean age 65.13 ± 7.08 years) with moderate and severe internal carotid artery stenosis underwent CAS with distal filter protection. Fibrolipid and fibrocalcified plaque morphology was determined by sonography according to the relative contribution of echogenic and echolucent material, and by multisection CT using plaque attenuation. There were 46.81% of patients with fibrolipid and 53.19% with fibrocalcified plaques. DWI was performed before and 24 hours after CAS.

RESULTS

Seven (14.89%) patients showed new lesions. Four (8.51%) had 6 new lesions inside the treated vascular territory. Three had a single lesion and 1 patient had 3 lesions (mean: 1.5 ± 1). Most lesions (66.66%) were subcortical, with a mean diameter of 9 mm (range 5-15 mm). All lesions occurred in the area supplied by the middle cerebral artery and were clinically silent. A significant relationship was found between plaque morphology and the appearance of new lesions. Patients with fibrolipid plaques had a significantly higher number of new lesions compared with patients with fibrocalcified plaques (P = .041). The absolute risk of new lesions in the fibrolipid group was 18.18%.

CONCLUSIONS

New ischemic lesions were observed in the treated vascular territory in 8.51% of patients. The appearance of new ischemic lesions was significantly related to the plaque morphology. Fibrolipid plaques were associated with higher numbers of new lesions.

Stenting versus medical treatment for severe symptomatic intracranial stenosis

BACKGROUND AND PURPOSE

Intracranial atherosclerosis is especially prevalent in Asians, but intracranial stent placement and medical treatment for severe intracranial stenosis are controversial. Thus, we compared long-term outcomes of these 2 therapeutic approaches in an Asian population.

MATERIALS AND METHODS

Patients with angiographically proved severe (≥70%) symptomatic intracranial atherosclerosis, with or without stent placement, were retrospectively reviewed at a single center between 2002 and 2009, with adjustments for age, sex, vascular risk factors, degree of baseline stenosis, and baseline functional status.

RESULTS

Of the 114 patients followed from 3 to 36 months (mean, 17.3 months) after initial diagnosis, 53 received 56 stents in addition to medical treatment (stent-placement group), and 61 matched patients received only medical treatment (medical group). Total clinical events, including stroke, TIA, and vascular death, were 12 (22.6%) and 15 (24.6%) in the stent-placement and medical groups, respectively (P = .99). The stent-placement group had significantly better functional outcomes than the medical group (94.3% versus 78.7% for mRS scores of 0-3, P = .045). Most events in the stent-placement group occurred within the first week of the periprocedural period (17.0%) as minor embolic or perforator infarctions, and the rate of events decreased thereafter (5.7%, P = .07). Stent placement over the perforator-rich MCA and BA independently predicted periprocedural events on multivariate regression analysis. In the medical group, events increased in frequency (21.7%) and severity with time.

CONCLUSIONS

Although the total ischemic event rate was similar in the 2 groups during a 3-year follow-up, the stent-placement group had a more favorable functional outcome despite minor periprocedural strokes.

Silent cortical neuronal damage in atherosclerotic disease of the major cerebral arteries

In atherosclerotic internal carotid artery (ICA) or middle cerebral artery (MCA) disease, hemodynamic compromise may cause selective neuronal damage manifested as loss of central benzodiazepine receptors (BZRs) in the normal-appearing cerebral cortex, without overt episode of stroke. To investigate the association of decreases in cortical BZRs with hemodynamic compromise and the effect of angiotensin receptor blockers (ARBs) on these receptors in patients whose atherosclerotic ICA or MCA disease is asymptomatic, we measured BZRs using positron emission tomography and (11)C-flumazenil in 79 patients with asymptomatic atherosclerotic ICA or MCA disease and no cortical infarction. Three-dimensional stereotactic surface projections were used to calculate the BZR index, a measure of abnormally decreased BZRs in the cerebral cortex within the MCA distribution. Multiple regression analysis showed this index to be positively correlated with the value of oxygen extraction fraction, with the presence of silent subcortical infarcts, and with the presence of ischemic heart disease, whereas it was negatively correlated with the treatment of hypertension with ARBs. In asymptomatic atherosclerotic ICA or MCA disease, hemodynamic compromise is associated with selective neuronal damage manifested as decreases in cortical BZRs in the noninfarcted cerebral cortex, whereas ARBs are associated with preservation of cortical BZRs.

Cold pre-conditioning neuroprotection depends on TNF-α and is enhanced by blockade of interleukin-11

Cold pre-conditioning reduces subsequent brain injury in small animals but the underlying mechanisms remain undefined. As hypothermia triggers systemic macrophage tumor necrosis factor alpha (TNF-α) production and other neural pre-conditioning stimuli depend on this cytokine, we reasoned that microglia and TNF-α would be similarly involved with cold pre-conditioning neuroprotection. Also, as slice cultures closely approximate their in vivo counterpart and include quiescent microglia, we used rat hippocampal slice cultures to confirm this hypothesis. Furthermore, inflammatory cytokine gene screening with subsequent PCR and immunostaining confirmation of targeted mRNA and related protein changes showed that cold pre-conditioning triggered a significant rise in TNF-α that localized to microglia and a significant rise in interleukin (IL)-11 that localized mainly to hippocampal pyramidal neurons and, more rarely, astrocytes. Importantly, co-stimulation with cold and IL-11, an anti-inflammatory cytokine that inhibits TNF-α expression, abrogated the otherwise evident protection. Instead, cold pre-conditioning coupled with blockade of IL-11 signaling further enhanced neuroprotection from that seen with cold pre-conditioning alone. Thus, physiological activation of brain pro-inflammatory cytokine signaling, and its amplification by inhibition of coincident anti-inflammatory cytokine signaling, may be opportune targets for the development of novel therapeutics that can mimic the protection seen in cold pre-conditioning.

Guidelines for patient selection and performance of carotid artery stenting

BACKGROUND

The endovascular treatment of carotid atherosclerosis with carotid artery stenting (CAS) remains controversial. Carotid endarterectomy remains the benchmark in terms of procedural mortality and morbidity. At present, there are no consensus Australasian guidelines for the safe performance of CAS.

METHODS

We applied a modified Delphi consensus method of iterative consultation between the College representatives on the Carotid Stenting Guidelines Committee (CSGC).

RESULTS

Selection of patients suitable for CAS needs careful consideration of clinical and patho-anatomical criteria and cannot be directly extrapolated from clinical indicators for carotid endarterectomy (CEA). Randomized controlled trials (including pooled analyses of results) comparing CAS with CEA for treatment of symptomatic stenosis have demonstrated that CAS is more hazardous than CEA. On current evidence, the CGSC therefore recommends that CAS should not be performed in the majority of patients requiring carotid revascularisation. The evidence for CAS in patients with symptomatic severe carotid stenosis who are considered medically high risk is weak, and there is currently no evidence to support CAS as a treatment for asymptomatic carotid stenosis. The use of distal protection devices during CAS remains controversial with increased risk of clinically silent stroke. The knowledge requirements for the safe performance of CAS include an understanding of the evidence base from randomized controlled trials, carotid and aortic arch anatomy and pathology, clinical stroke syndromes, the differing treatment options for stroke and carotid atherosclerosis, and recognition and management of periprocedural complications. It is critical that all patients being considered for a carotid intervention have adequate pre-procedural neuro-imaging and an independent, standardized neurological assessment before and after the procedure. Maintenance of proficiency in CAS requires active involvement in surgical/endovascular audit and continuing medical education programs. These standards should apply in the public and private health care settings.

CONCLUSION

These guidelines represent the consensus of an inter-collegiate committee in order to direct appropriate patient selection and the range of cognitive and technical requirements to perform CAS. Advances in endovascular technologies and the results of randomized controlled trials will guide future revisions of these guidelines.

Is the surgical repair of unruptured atherosclerotic aneurysms at a higher risk of intraoperative ischemia?

BACKGROUND

The incidence of ischemia might be increased in the surgical repair of atherosclerotic unruptured aneurysms compared to non-atherosclerotic aneurysms. The atherosclerotic wall might increase the occurrence of thrombembolic events or its rigidity might endanger the occlusion of perforators within the aneurysm vicinity.

METHODS

87 patients (53 patients without and 34 patients with atherosclerotic unruptured aneurysms, 50.5 ± 9.7 years) were analyzed for severity of atherosclerosis within the aneurysm and the aneurysm bearing vessel, surgical maneuvers, intraoperative alterations in evoked potentials and clinical and neuroradiological results.

RESULTS

Temporary vessel occlusion (25% vs. 50%, p = 0.021), repositioning of a permanent clip (21% vs. 56%, p = 0.001) and aneurysm remnants (2% vs. 18%, p = 0.012) occurred more often in patients with atherosclerotic aneurysms. At 6 months, 3/34 patients with atherosclerosis (8.8%) had an unfavorable outcome, all patients without atherosclerosis had a favorable outcome (p = 0.056).

CONCLUSION

The surgical repair of unruptured aneurysms is safe but patients with atherosclerotic altered vessels and aneurysms accounted to a minor increase in unfavorable outcome and an increased risk of morbidity at 6 months postoperatively. This factor should be taken into consideration when performing surgery of atherosclerotic, unruptured aneurysms.

The (Un)Importance of Cerebral Microemboli

Background: The use of cardiopulmonary bypass (CPB) is associated with cerebral microemboli. Cognitive decline after cardiac surgery has therefore always been attributed to the use of CPB. However, randomized studies comparing coronary bypass surgery with and without CPB failed to establish a clear cognitive benefit of avoiding CPB. The aim of this analysis was to systematically review the studies that directly assessed the association between cerebral microemboli and cognitive decline after cardiac surgery. Methods: The electronic database of PubMed of the National Library of Medicine from 1980 until 2009 was searched to identify relevant literature. Search terms related to “cardiac surgery,” “microemboli,” and “cognitive decline” were used. Studies were reviewed independently by 2 reviewers and relevant articles were included completely if they matched the selection criteria. This review included studies in adult cardiac surgical patients reporting both a measure of cerebral embolic load and cognitive outcomes. Results: The literature search yielded 423 different titles, of which 22 met the selection criteria. All 22 studies used neuropsychological tests to determine cognitive outcome. Seven studies used postoperative (diffusion-weighted) magnetic resonance imaging (MRI) to detect cerebral emboli and 15 studies used intraoperative transcranial Doppler imaging. In 1 MRI study and 5 Doppler studies, an association was found between the number of cerebral emboli and the risk of postoperative cognitive decline. In 15 studies, such an association could not be established. One study did not assess the direct relation between microemboli and cognitive decline. Conclusion: This systematic review could neither confirm nor rule out a causal link between emboli from CPB and postoperative cognitive decline.

Guidelines for patient selection and performance of carotid artery stenting

The endovascular treatment of carotid atherosclerosis with carotid artery stenting (CAS) remains controversial. Carotid endarterectomy (CEA) remains the benchmark in terms of procedural mortality and morbidity. Consensus Australasian guidelines for the safe performance of CAS were developed using the modified Delphi consensus method of iterative consultation. Selection of patients suitable for CAS needs careful consideration of clinical and patho-anatomical criteria. Randomised controlled trials and pooled analyses have demonstrated that CAS is more hazardous than CEA. The CGSC therefore recommends that CAS should not be performed in the majority of patients requiring carotid revascularisation. There is currently no evidence to support CAS as a treatment for asymptomatic carotid stenosis. The use of distal protection devices during CAS remains controversial with increased risk of clinically silent stroke. The knowledge requirements for the safe performance of CAS include an understanding of the evidence base from randomised controlled trials, carotid and aortic arch anatomy and pathology, and recognition and management of periprocedural complications. It is critical that all patients being considered for a carotid intervention have adequate pre-procedural neuroimaging and peri-procedural, independent, neurological assessment. Maintenance of proficiency in CAS requires active involvement in surgical/endovascular audit and continuing medical education programmes. These standards should apply in the public and private health-care settings. These guidelines represent the consensus of an intercollegiate committee in order to direct appropriate patient selection to perform CAS. Advances in endovascular technologies and the results of randomised controlled trials will guide future revisions of this document.

Silent and Apparent Cerebral Ischemia After Percutaneous Transfemoral Aortic Valve Implantation

Background— The risk of stroke after transfemoral aortic valve implantation (TAVI) due to dislodgement and subsequent embolization of debris from aortic arch atheroma or from the calcified valve itself ranges between 2% and 10%. The rate of clinically silent cerebral ischemia is unknown but may be even higher.

Methods and Results— Thirty-two patients who underwent TAVI with the use of a balloon-expandable (n=22) or self-expandable (n=10) stent valve prosthesis were included in this descriptive study and compared with a historical control group of 21 patients undergoing open surgical aortic valve replacement. Periprocedural apparent and silent cerebral ischemia was assessed by neurological testing and serial cerebral diffusion-weighted magnetic resonance imaging at baseline, at 3.4 (2.5 to 4.4) days after the procedure, and at 3 months. TAVI was successful in all patients. After the procedure, new foci of restricted diffusion on cerebral diffusion-weighted magnetic resonance imaging were found in 27 of 32 TAVI patients (84%) and were more frequent than after open surgery (10 of 21 patients [48%]; P =0.011). These lesions were usually multiple (1 to 19 per patient) and dispersed in both hemispheres in a pattern suggesting cerebral embolization. Volumes of these lesions were significantly smaller after TAVI than after surgery (77 [59 to 94] versus 224 [111 to 338] mm 3 ; P <0.001). There were neither measurable impairments of neurocognitive function nor apparent neurological events during the in-hospital period among TAVI patients, but there was 1 stroke (5%) in the surgical patient group. On 3-month follow-up diffusion-weighted magnetic resonance imaging, there were no new foci of restricted diffusion, and there was no residual signal change associated with the majority (80%) of the foci detected in the periprocedural period.

Conclusions— Clinically silent new foci of restricted diffusion on cerebral magnetic resonance imaging were detected in almost all patients (84%) undergoing TAVI. Although typically multiple, these foci were not associated with apparent neurological events or measurable deterioration of neurocognitive function during 3-month follow-up. Further work needs to be directed to determine the clinical significance of these findings in a larger patient population.

Acute Brain Infarcts After Spontaneous Intracerebral Hemorrhage

Background and Purpose— We aimed to determine the prevalence of acute brain infarcts using diffusion-weighted imaging (DWI) in patients with spontaneous intracerebral hemorrhage (ICH).

Methods— We collected data on consecutive patients with spontaneous ICH admitted to our institution between August 1, 2006 and December 31, 2008 and in whom DWI was performed within 28 days of admission. Patients with hemorrhage attributable to trauma, tumor, aneurysm, vascular malformation, and hemorrhagic conversion of arterial or venous infarction were excluded. Restricted diffusion within, contiguous with, or immediately neighboring the hematoma or chronic infarcts was not considered abnormal. Using multivariable logistic regression, we evaluated potential predictors of DWI abnormality including clinical and radiographic characteristics and treatments. A probability value <0.05 was considered significant in the final model.

Results— Among 118 spontaneous ICH patients (mean 59.6 years, 47.5% male, and 31.4% white) who also underwent MRI, DWI abnormality was observed in 22.9%. The majority of infarcts were small (median volume 0.25 mL), subcortical (70.4%), and subclinical (88.9%). Factors independently associated with DWI abnormality were prior ischemic stroke ( P =0.002), MAP lowering by ≥40% ( P =0.004), and craniotomy for ICH evacuation ( P =0.001).

Conclusion— We found that acute brain infarction is relatively common after acute spontaneous ICH. Several factors, including aggressive blood pressure lowering, may be associated with acute ischemic infarcts after ICH. These preliminary findings require further prospective study.

Ambulatory recorded ST segment depression on ECG is associated with lower cognitive function in healthy elderly men

ST segment depression (STDE) has been found to be associated with cardiovascular disease in the elderly. Studies of the relation of ambulatory STDE to cognitive function in elderly persons aged 80 years or above is lacking.

OBJECTIVE

To study the association between STDE and cognition.

DESIGN AND PARTICIPANTS

A cross-sectional cohort study of 88 81-year-old men from the population study "Men born in 1914" investigated in an outpatient research clinic. Measurements included ambulatory 24-hour electrocardiogram (ECG) monitoring and a cognitive test battery of six tests. Proportion of lower cognitive function was calculated for each test in relation to STDE during the day and at night-time.

RESULTS

Fifty-eight percent of the men had STDE and a higher proportion with low visuospatial cognitive function was found among those with STDE compared to the others (84% vs 59%; p = 0.014). A significant trend was noted for subjects without STDE compared to STDE night-time less than 60 minutes and night-time more than 60 minutes for spatial and verbal cognitive functions (p = 0.022). No trends were noted for STDE daytime. Maximal STDE during night showed similar association to spatial function (Benton Visual Retention test, r = -0.26; p = 0.028). Even when seven subjects with a history of stroke were excluded, the occurrence of STDE was associated to lower visuospatial cognitive function compared to those without STDE (87% vs 57%; p = 0.004).

CONCLUSION

ST segment depression on ECG is common among elderly men and might be a vascular risk factor for cognitive deterioration.

Molecular mechanisms of thrombus formation in ischemic stroke: novel insights and targets for treatment

In ischemic stroke, treatment options are limited. Therapeutic thrombolysis is restricted to the first few hours after stroke, and the utility of current platelet aggregation inhibitors, including GPIIb/IIIa receptor antagonists, and anticoagulants is counterbalanced by the risk of intracerebral bleeding complications. Numerous attempts to establish neuroprotection in ischemic stroke have been unfruitful. Thus, there is strong demand for novel treatment strategies. Major advances have been made in understanding the molecular functions of platelet receptors such as glycoprotein Ib (GPIb) and GPVI and their downstream signaling pathways that allow interference with their function. Inhibition of these receptors in the mouse stroke model of transient middle cerebral artery occlusion prevented infarctions without increasing the risk of intracerebral bleeding. Similarly, it is now clear that the intrinsic coagulation factor XII (FXII) and FXI play a functional role in thrombus formation and stabilization during stroke: their deficiency or blockade protects from cerebral ischemia without overtly affecting hemostasis. Based on the accumulating evidence that thrombus formation and hemostasis are not inevitably linked, new concepts for prevention and treatment of ischemic stroke may eventually emerge without the hazard of severe bleeding complications. This review discusses recent advances related to antithrombotic strategies in experimental stroke research.

The Angioguard embolic protection device

Endovascular management of cardiovascular disease is quickly becoming a more popular treatment. The effectiveness in using embolic protection devices (EPDs), such as the Angioguard XP filter, during carotid artery stenting (CAS) is a topic of ongoing controversy and scrutiny. Early clinical results indicate that EPDs can reduce complications associated with CAS. However, the incidence of stroke and postprocedural embolic events are statistically similar when comparing CAS with the gold standard in carotid stenosis repair, carotid endarterectomy (CEA). The focus of this manuscript is the critical evaluation of Angioguard XP with respect to numerous in vitro and ex vivo experiments, and clinical trials that have been conducted by the authors and other researchers to investigate the efficacy of EPDs with the objective of suggesting engineering design considerations for future generations of these devices. Angioguard XP has had mixed performance outcomes in in vitro testing reported in the literature. In our laboratory, this device had undesirable measures of performance in bench-top testing protocols using in vitro flow models. Technical considerations relevant to design of EPDs, such as ideal pore size, effective wall apposition in tortuous geometry and maximization of capture efficiency have not been addressed adequately in the literature. It is likely that in the future both CAS and CEA will coexist as potential forms of treatment in the clinical management of cerebrovascular disease.

Late evaluation of silent cerebral ischemia detected by diffusion-weighted MR imaging after filter-protected carotid artery stenting

BACKGROUND AND PURPOSE

Postoperative diffusion-weighted MR imaging (DWI) often discloses new lesions after carotid artery stent placement (CAS), most of them asymptomatic. Our aim was to investigate the fate of these silent ischemic lesions.

MATERIALS AND METHODS

We prospectively studied 110 patients undergoing protected transfemoral CAS, 98 of whom underwent DWI before and after the intervention. Patients in whom DWI disclosed silent postoperative lesions also had delayed MR imaging. Preoperative, postoperative, and delayed scans were compared.

RESULTS

Of the 92 patients without postoperative symptoms, DWI disclosed 33 new silent ischemic lesions in 14 patients (15.2%), 13 of whom (30 lesions) underwent delayed MR imaging after a mean follow-up of 6.2 months. In 8 of these 13 patients (61%), MR imaging disclosed 12 persistent lesions (12/30, 40%). The reversibility rate depended significantly on the location (cortical versus subcortical) and size (0-5 versus 5-10 mm) of the lesions (P < .05 by chi(2) test).

CONCLUSIONS

Because many silent ischemic lesions seen on postoperative DWI after CAS reverse within months, the extent of permanent CAS-related cerebral damage may be overestimated.

New brain lesions after carotid stenting versus carotid endarterectomy: a systematic review of the literature

BACKGROUND AND PURPOSE

Against the background of a relatively low rate of clinical events during carotid angioplasty and stenting (CAS) or carotid endarterectomy (CEA), diffusion-weighted imaging (DWI) is increasingly being used to compare the incidence of new ischemic lesions after both procedures. In addition, DWI may also provide a means of defining the role of different CAS techniques on this adverse outcome. Therefore, we performed a PubMed search and systematically analyzed all peer-reviewed studies published between January 1990 and June 2007 reporting on the occurrence of new DWI lesions after CAS or CEA. Summary of Review- In 32 studies comprising 1363 CAS and 754 CEA procedures, the incidence of any new DWI lesion was significantly higher after CAS (37%) than after CEA (10%) (P<0.01). Similar results were obtained in a meta-analysis focusing on those studies directly comparing the incidence of new DWI lesions after either CEA or CAS (OR, 6.1; 95% CI, 4.19 to 8.87; P<0.01). The use of cerebral protection devices (33% vs 45% without; P<0.01) and closed-cell designed stents during CAS (31% vs 51% with open-cell stents; P<0.01), as well as selective versus routine shunt usage during CEA (6% vs 16%; P<0.01) significantly reduced the incidence of new ipsilateral DWI lesions.

CONCLUSIONS

New DWI lesions occur more frequently after CAS than after CEA. However, technical advances mainly in the field of endovascular therapy potentially reduce the incidence of these adverse ischemic events. In this scenario, DWI appears to be an ideal tool to compare and further improve both techniques.

Cognitive outcomes five years after not undergoing coronary artery bypass graft surgery

BACKGROUND

Patients with coronary artery disease who underwent coronary artery bypass graft surgery have a high risk of cognitive decline 5 years after the procedure. It is conceivable that this is not caused by the operation, but by natural aging.

METHODS

Psychologists repeatedly administered a battery of seven neuropsychological tests with eight main variables to 112 subjects without known coronary artery disease, with a time interval of 5 years. Cognitive decline was defined as deterioration in performance beyond normal variation in at least two of the eight main variables. The incidence of cognitive decline in the control subjects was compared with the incidence of cognitive decline in the 281 participants of the Octopus Study, who underwent coronary artery bypass graft surgery 5 years earlier. Patients and control subjects were age-matched.

RESULTS

After 5 years, cognitive outcome could be determined in 99 of 112 control subjects (88%) and 240 of 281 coronary artery bypass graft surgery patients (85%). Cognitive decline was present in 82 (34.2%) of 240 coronary artery bypass graft surgery patients and in 16 (16.2%) of 99 control subjects (crude odds ratio, 2.69; 95% confidence interval, 1.48 to 4.90). However, after correction for differences in age, sex, education, and baseline comorbidity between the patients and the control subjects, the odds ratio was 1.37 (95% confidence interval, 0.65 to 2.92).

CONCLUSIONS

We were unable to demonstrate that patients who underwent coronary artery bypass graft surgery have more cognitive decline after 5 years than control subjects without coronary artery disease.

Targeting the brain: rationalizing the novel methods of drug delivery to the central nervous system

Drug delivery to the brain has remained one of the most vexing problems in translational neuroscience research. This review rationalizes the strategies to target drugs to the brain. Factors such as the speed of intervention, the scale of intervention, the state of BBB, and the permissible risks, will all be critical in deciding how best to deliver drugs to a target site in the brain for a specific clinical situation.

Technology insight: brain MRI and cardiac surgery--detection of postoperative brain ischemia

Annually, an estimated 1 million patients undergo heart surgery worldwide. Unfortunately, stroke continues to be a frequent complication of cardiac surgery, with the specific cerebrovascular risk depending upon the particular surgical procedure performed. Neuroimaging has an integral role in the initial evaluation and management of patients who present with acute stroke symptoms following cardiac surgery. The aim of this paper is to review the role brain MRI has in detecting postoperative brain ischemia in these patients. Multimodal MRI--using diffusion-weighted MRI (DWI), perfusion-weighted MRI, and gradient-recalled echo imaging--has an excellent capacity to identify and delineate the size and location of acute ischemic strokes as well as intracerebral hemorrhages. This differentiation is critical in making appropriate treatment decisions in the acute setting, such as determining patient eligibility for thrombolytic or hemodynamic therapies. At present, DWI offers prognostic value in patients with strokes following cardiac surgery. Additionally, DWI could be a valuable tool for evaluating stroke preventive measures as well as therapeutic interventions in patients undergoing CABG surgery.

Widespread effects of hyperintense lesions on cerebral white matter structure

OBJECTIVE

Hyperintense lesions are a common finding on neuroimaging and are associated not only with aging, medical illness, and some invasive medical procedures, but also with neurologic and psychiatric morbidity. We hypothesized that hyperintense lesions are associated with alterations in white matter structure beyond the visible lesion boundaries as assessed with diffusion tensor imaging (DTI).

SUBJECTS AND METHODS

Eighty-two neurologically intact older individuals completed brain MRI with DTI. DTI scans were analyzed using regions of interest placed in normal-appearing white matter to measure fractional anisotropy and diffusivity in the white matter of the frontal lobe, the genu of the corpus callosum, and the internal capsule. Hyperintense lesions volumes were measured separately in subcortical gray matter and anterior white matter through a semiautomated segmentation program. The relationship between lesion volumes and DTI measures was examined while controlling for patient age, patient sex, and total cerebral volume.

RESULTS

Greater anterior white matter lesion volumes were associated with higher diffusivity and lower anisotropy in the white matter of the dorsolateral prefrontal cortex and with higher diffusivity of the internal capsule and white matter lateral to the anterior cingulate cortex. Gray matter lesion volumes were associated with higher diffusivity in the genu of the corpus callosum and the internal capsule.

CONCLUSION

Ischemic hyperintense lesions are associated with widespread effects on the structure of the frontal lobe white matter and central white matter structures. This may reflect effects of lesions on neural circuits or identification of white matter changes that have not yet become visible on conventional MRI.

Intra-arterial drug delivery: a concise review

The therapeutic potential of intra-arterial (IA) drug delivery to the brain has received limited attention in the last decade. In the 1980s, efforts to treat brain tumors with IA chemotherapy, the leading application of this technology, yielded modest results. Poor control of tissue drug concentrations and the potential risk of permanent neurologic injury further prevented the wider use of IA drugs. Yet, IA drugs were anecdotally used for treating a wide spectrum of brain diseases. Recent advances in endovascular technology and the increased safety of angiographic procedures now compel us to reevaluate IA drug delivery. This review describes the pharmacologic principles, applications, and pitfalls of IA drug delivery to the brain.